Matrix is a harmless memory resident polymorphic virus. It works only under Windows 95 and 98. It stays resident in the Windows memory as a device driver (VxD) by switching from application mode to Windows kernel mode (Ring3->Ring0). It hooks disk files access functions and infects PE executable files with EXE and SCR extensions. The virus affects DOS's COM files, also.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
While infecting a PE EXE file, the virus encrypts itself and writes itself to the end of the file. The virus patches the startup code of the program with a short routine that passes control to the main virus code. While affecting DOS's COM files, the virus writes a short routine to the end of the file which has no infection abilities, but just displays a message on the 7th of July:
vWake up, Neo... The Matrix has you... w9x.mATRiX
The virus also changes the C:\WINDOWS\WIN.COM file in the same way. On the 6th of April, the virus modifies the following Registry key:
HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer NoClose = 1
As a result the user cannot switch off the computer. You can get rid of this key by downloading and runnung the special REG file that is available on our ftp site:
The virus also deletes several anti-virus database files:
AVP.CRC, ANTI-VIR.DAT, IVB.NTZ, CHKLIST.MS.
The virus contains some text strings:
<w9x.mATRiX.3597.xxxxxxx & MyLittlePoly.1534 by LiFEwiRE [sHAD0WvX]>
where 'xxxxxxx' is the "generation" number of the virus.
Please use the DOS version of FSAV and the latest updates to safely remove this virus. Use the above mentioned REG file to remove the trojanized Registry entry.
Technical Details: AVP Team, F-Secure AV Team